"I didn't want to touch one because you never know what can sting you on the beach, but I did poke it with my toes and it's squishy, like a sponge. They look like alien eggs or something."

Local resident, Jenny Zhang, further added: "About three days ago, there were a few egg-shaped balls but then today, they were much bigger and everywhere on the beach.

While locals in Dee Why explored extra-terrestrial origins, scientists clarify that the sponge-like spheres are in fact seaweed that cluster together in the form of an egg to protect themselves from predators.

"I've seen similar things - sometimes dead sea grass can roll around and form balls like underwater tumbleweeds but that's made of dead material and these look to be living. It is a habit known as "aegagropilious", where the algae is free living (not on rocks) and forms into spherical balls."